As an image display device substitutable for liquid crystal display (LCD), image display devices with the use of technology such as an electrophoresis method, an electro-chromic method, a thermal method, dichroic-particles-rotary method are proposed.
As for these image display devices, it is conceivable as inexpensive visual display device of the next generation from a merit having wide field of vision close to normal printed matter, having smaller consumption with LCD, spreading out to a display for portable device, and an electronic paper is expected. Recently, an electrophoresis method is proposed that microencapsulates dispersion liquid made up with dispersion particles and coloration solution and disposes the liquid between faced substrates.
However, in the electrophoresis method, there is a problem that a response rate is slow by the reason of viscosity resistance because the particles migrate among the electrophoresis solution. Further, there is a problem of lacking imaging repetition stability, because particles with high specific gravity of titanium oxide are scattered within solution of low specific gravity, it is easy to subside, difficult to maintain a stability of dispersion state. Even in the case of microencapsulation, cell size is diminished to a microcapsule level in order to make it hard to appear; however, an essential problem was not overcome at all.
Besides the electrophoresis method using behavior in the solution, recently, a method wherein electro-conductive particles and a charge transport layer are installed in a part of the substrate without using solution is proposed. [The Imaging Society of Japan, “Japan Hardcopy '99” (Jul. 21-23, 1999) Transaction Pages 249-252.] However, the structure becomes complicated because the charge transport layer and further a charge generation layer are to be arranged. In addition, it is difficult to constantly dissipate charges from the electro-conductive particles, and thus there is a drawback on the lack of stability.
However, in the case such that a surface of a substrate, to which particles or liquid powders to be sealed having an excellent mobility are contacted, has such a state that a material constituting the substrate is exposed as it is, durability for a repetition use is insufficient when it is used as the image display panel. That is, even in the particles and the liquid powders, there occurs a phenomenon during the repetition use such that the particles or the liquid powders are adhered to the surface of the substrate and don't move, and there is a problem such that a contrast of the image is deteriorated (task to be solved by a first aspect of the invention).
Moreover, in the case such that a surface of a substrate or a partition wall, to which particles or liquid powders to be sealed having an excellent mobility are contacted, has such a state that a material constituting the substrate or the partition wall is exposed as it is, durability for a repetition use is insufficient when it is used as the image display panel. That is, even in the particles and the liquid powders, there occurs a phenomenon during the repetition use such that the particles or the liquid powders are adhered to the surface of the substrate or the partition wall and don't move, and there is a problem such that a contrast of the image deteriorates. As a result, it is insufficient on the durability for the repetition use (task to be solved by the second to the fourth aspects of the invention).
In order to solve the problems mentioned above, there is known an image display device which comprises an image display panel, in which one or more groups of particles are sealed in a plurality of cells formed by partition walls between two substrates, at least one of two substrates being transparent, and, in which the particles, to which an electrostatic field produced by electrodes provided to both of the substrates is applied, are made to fly and move so as to display an image by utilizing Coulomb's force.
In the image display device mentioned above, an opening rate of the cell is varied due to a shape of the partition wall, for example, when the partition wall is formed on a glass substrate by means of a photo-resist and a plurality of cells are constructed between two substrates. Therefore, in the case such that a ratio between a height Lh and a width Lw of the partition wall is set at a value out of an adequate range, there occurs a decrease of the opening rate and a deterioration of a manufacturing property. This problem occurs in the same manner even in an image display device which comprises an image display panel in which liquid powders composed of a solid material stably floating as a dispersoid in a gas and exhibiting a high fluidity in an aerosol state or particles are sealed in a plurality of cells formed by partition walls between opposed substrates, at least one substrate being transparent, and, in which the liquid powders or the particles, to which an electrostatic field is applied from two kinds of electrodes having different potentials, are made to fly and move so as to display an image (task to be solved by a fifth aspect of the invention).
Moreover, in the image display device mentioned above, it is possible to control humidity in the device preferably without using a drying agent, for example, by adding a drying function to the partition wall. However, when the partition wall is made of a material having a water absorption property in order to achieve the drying function mentioned above, it is important to control a water absorption rate of the partition wall. In the case such that a water absorption rate of the partition wall is set at a value out of an adequate range, there occurs a case such that a water absorption effect becomes insufficient or water is excessively absorbed during a device assembly process, so that a display property is affected. This problem occurs in the same manner even in an image display device which comprises an image display panel in which liquid powders composed of a solid material stably floating as a dispersoid in a gas and exhibiting a high fluidity in an aerosol state or particles are sealed in a plurality of cells formed by partition walls between opposed substrates, at least one substrate being transparent, and, in which the liquid powders or the particles, to which an electrostatic field is applied from two kinds of electrodes having different potentials, are made to fly and move so as to display an image (task to be solved by a sixth aspect of the invention).